import re

input_str = """
RE_PING_HENG_RE_PING_HENG_E116/SUM(RE_PING_HENG_E106:RE_PING_HENG_RE_PING_HENG_E116)*100/SUM(a+b)
"""

"""
SUM()括号内的内容
"""
p = re.compile(r"SUM[(](.*?)[)]", re.S) #最小匹配
result = re.findall(p, input_str)
print(result)